1. Field of the Invention
This invention pertains generally to a spectrum bandwidth tuning apparatus and more specifically to a device for dynamic dispersion compensation in an optical link utilizing Bragg gratings.
2. Description of the Prior Art
Chromatic dispersion is an impairment to transmission of optical pulses in optical media, such as an optical fiber. Typically dispersion impairments in optical communication systems are alleviated by the use of dispersion compensating fibers, which are placed at strategic locations in an optical link. This method known as dispersion management has been successful but requires that the optical paths remain relatively static. However, in optical networks of the future the path that an optical signal takes within the network will be a dynamic parameter due to reconfigurability requirement. Additionally, the tolerances for dispersion compensation becomes tighter as the bit rate increases. These two effects combine to force a requirement in optical networks to have dynamic or tunable dispersion compensating devices at various locations in the network.
Dynamically reconfigurable dispersion compensating devices are being actively developed due to the need for dynamic adjustment of dispersion in future high bit rate optical networks. Dynamic dispersion compensation is necessary due to unpredictable variations in the optimal dispersion map caused by network reconfiguration, fiber nonlinearities and signal power variations which may occur due to changes in optical amplifier gain flatness or due to the insertion of new optical networking elements, for instance a reconfigurable add/drop multiplexer. Dynamic dispersion compensation becomes more significant as optical networks progress towards higher bit rates as the dispersion tolerance reduces dramatically (as the square of the bit rate). In order to mitigate this problem, development of high performance, reliable, dynamic chromatic dispersion compensating devices is important.
The object of this invention is to provide a device that effectively accomplishes dynamic dispersion compensation in optical links.
Another object of this invention is to provide a device for reconfigurable, high-speed optical networks of the future.
Another object of this invention is to provide a device for performing a critical dispersion compensation measurement in a short pulse.
These and other objectives are achieved by a bandwidth tunable fiber Bragg grating (FBG) device wherein tuning is performed by placing a grating in a compliant material, which is transversely loaded to create longitudinal strain through the Poisson effect in compliant materials. Careful application of various load magnitudes along the length of the grating through the compliant material creates a strain gradient along the length of the grating, which chirps the grating thus resulting in altering the bandwidth of the grating. Tuning the grating bandwidth results, effectively, in tuning the dispersion of light being reflected off the grating. Insertion of such a device in the optical link allows for dynamic dispersion compensation in the link. The ability of the device to xe2x80x98dial-inxe2x80x99 a desired amount of dispersion is what makes it valuable in reconfigurable optical networks.